The aim of this investigation is to improve the method for calculating design wind speed used for wave run up at water reservoirs. It is focused on the relation between extreme flood and wind events, and between wind speed and duration.

Water flow data from fourteen Norwegian river basins and wind data from neighbouring airfields are correlated. Some positive correlation is found for areas situated at the coastal side of the mountains where a further analysis is carried out. Extreme value analysis of the wind and flood series provides estimates of T-year events for each of the two variables. The best-fitted equation linking the square of the maximum 10-minute wind speeds to the daily mean water flow is established. It is observed that the expected wind speed during the 1000-year daily flood event has approximately one year return period. The risk for higher wind speed is high, so the effect of adding 1 and 1.65 standard deviations of the maximum wind speed is assessed, increasing the expected return period to 5 and 20 years respectively.

Continuous records of 10-minute wind speed are used to establish transfer coefficients from the extreme 10-minute value to durations of 20 minutes to 6 hours.